Project Summary Anxiety disorders are highly prevalent in childhood and are associated with substantial impairment and disability. Symptoms of anxiety are widespread in preschoolers with ASD, limiting their learning and social interaction opportunities above and beyond difficulties related to core autism symptoms. Our preliminary work suggests that temperamental precursors of anxiety are already elevated in the second year of life in ASD. However, knowledge about the mechanisms underlying the emergence of anxiety symptoms in ASD remains limited. This project will experimentally quantify attentional, affective, behavioral, physiological, and temperamental factors associated with anxiety in 4-year-olds with ASD (n=160), other developmental disorders and concerns (ATYP, n=80), and typical development (TYP, n=80). We will investigate the associations between affective attentional biases to threat (ABT) and emotional-regulatory functions as well as the hypothesized, but relatively unexplored, role of these features in emerging anxiety in ASD. ABT represents a rapid attentional response to threat that is evidenced by longer latencies required to decouple attention from threatening stimuli. ABT is among the best-replicated neurobehavioral markers of clinical and subclinical anxiety. Decreasing this bias lowers anxiety symptoms in school-age children, implicating ABT in maintenance of anxiety. Give that attentional system has been implicated in ASD, ABT offers an unexplored but highly innovative and generative framework for investigating mechanisms underlying the emergence of anxiety in very young children with ASD. The key questions in this proposal are: (1) Are children with ASD more biased toward or away from threat than other 4-year-olds? (2) Is ABT associated with anxiety severity in 4-year-olds with and without ASD? (3) What role do the facets of ABT play in the emergence of anxiety symptoms from 2 to 4 years? (4) Given the heterogeneity of anxiety expression in early childhood, can we identify homogeneous subgroups based on neurobehavioral and physiological measures across diagnostic categories that will inform about unique underlying mechanisms and novel treatment targets or strategies? To answer these questions, we will evaluate anxiety-related aspects of attention in response to threat using an eye-tracking attention disengagement task developed and tested in our lab. We will also examine in vivo reactivity to threat at affective, attentional, and physiological levels. Combining these multimodal indices of response to threat will allow for quantification of anxiety-related features in an unparalleled manner and evaluation of each feature's unique contributions to clinical phenotypes, at the time when anxiety symptoms first become apparent. By focusing our investigation on 4-year-olds we aim to identify, essential from a translational standpoint, the early ?developmental tethers? that bias children's development toward maladaptive pathways. Furthermore, identifying subgroups based on neurocognitive attentional and physiological responses may contribute to the development of a neuroscience-based approach to classification of anxiety disorders in preschoolers.